Abstract
This report discusses the cast hemispherical core dies for the hot extrusion of the hollow shaped aluminum alloys. The hemispherical core die is casted in SKD 61. The end face of the core of this die is hemispherical on the entry side of the billet. The maximum tensile stress appearing around the root of a mandrel of the core is remarkably reduced in comparison with a port-hole die, which results in suppresion of crack initiation. The solidification simulation was used for the purpose of predicting the solidification defects and increasing the temperature gradient at the point of tensile stress. The hemispherical cast dies with the temperature gradient of more than 303 K/cm had the same high-temperature stress characteristics (according to the tensile test piece, which is cut from the cast die) and demonstrated the same extrusion features as that of forged hemispherical core dies. By using this type of cast hemispherical core die, the raw material weight is 38.3 % of a forged hemispherical core die. Moreover, the die forming time is shortened by 50 %.
